Photosensitive composition

ABSTRACT

A radiation sensitive composition useful as a photoresist containing a resin composition and a radiation sensitive material, wherein the resin composition comprises a mixture of two or more resins different from each other by at least 0.03 in refractive index or comprises a resin component of an alkali-soluble resin and a resin additive of a resin working as a dissolution inhibitor for the radiation sensitive composition, such as an acrylic polymer, a methacrylic polymer or a styrenic polymer. A dissolution rate in a 2.38 weight-% aqueous tetramethylammonium hydroxide solution of the radiation sensitive composition is preferably 5000 Å/min or less. Use of these resin compositions enable one to reduce the amount of the quinonediazide radiation sensitive agents to be used and obtain a radiation sensitive composition which has both high sensitivity and highly normalized film remaining characteristics.

TECHNICAL FIELD

This invention relates to a radiation sensitive composition comprising aresin composition and a radiation sensitive material and, moreparticularly, to a radiation sensitive composition suitably usable as aphotoresist material in manufacturing a semiconductor device such as LSIand a flat panel display such as a liquid crystal display (LCD) etc.,and like use.

BACKGROUND ART

In the wide field of manufacturing semiconductor integrated circuitssuch as LSI, producing FPD, manufacturing a circuit substrate forthermal head etc., and like use, photolithography technique has so farbeen employed for forming microelements or conducting fine processing.In the photolithography technique, a positive or negative-workingradiation sensitive composition comprising a resin component and aradiation sensitive material is used for forming a resist pattern. Ofthese radiation sensitive compositions, those compositions comprising analkali-soluble resin and a radiation sensitive material ofquinonediazide compound are popularly used as the positive-workingradiation sensitive compositions. As such compositions, there aredescribed compositions having different formulations as, for example,‘novolak resin/quinonediazide compound’ in many documents such asJapanese Examined Patent Publication No. S54-23570 (U.S. Pat. No.3,666,473), Japanese Examined Patent Publication No.56-30850 (U.S. Pat.No. 4,115,128), Japanese Unexamined Patent Publication Nos. S55-73045and S61-205933, etc.

These compositions comprising a novolak resin and a quinonediazidecompound have so far been studied and developed with respect to bothnovolak resins and radiation sensitive materials. In respect of novolakresins, there have been developed novel resins. In addition, radiationsensitive compositions having excellent properties have also beenobtained by improving properties of conventionally known resins. Forexample, there are disclosed techniques providing a radiation sensitivecomposition having excellent properties by using a novolak resin with aparticular molecular weight distribution in Japanese Unexamined PatentPublication Nos. S60-140235 and H01-105243 and by using a novolak resinfrom which low-molecular-weight components of the resin has been removedby fractionation in Japanese Unexamined Patent Publication Nos.S60-97347, S60-189739 and Japanese Patent Publication No. 2590342.Further, as the negative-working radiation sensitive composition, acomposition comprising a novolak resin, an alkoxymethylated melamine asa cross-linking agent and a halogenated triazine as an acid generator(Japanese Unexamined Patent Publication No. H5-303196) can be mentioned.Up to now, radiation sensitive compositions having various compositionshave been developed, and as a result of the improvement of thecharacteristics of these radiation sensitive compositions, a largenumber of radiation sensitive compositions have been put into practice.

On the other hand, degree of integration in semiconductor elements havebeen increased year by year and, in the manufacture of semiconductorelements or the like, processing of patterns with a line width of lessthan sub-micron order has become required. However, conventionally knownradiation sensitive compositions can not satisfy enough theserequirements in the prior art described above. Further, the large-sizingof the mother glass is advancing in the production of display surface ofLCD etc. When the conventional radiation sensitive composition is usedas the resist material, there arise the following problems withlarge-sizing of a mother glass:

That is, first, there is mentioned the problem of sensitivity of theresist as large-sizing of the mother glass. This is because thefrequency of pattern exposure by the exposure device is increased as thesubstrate is large-sized and when the conventional radiation sensitivecomposition is used, the throughput (yield per unit time) in productionis lowered. For improvement of the throughput, the higher sensitizationof the resist is required.

In order to meet the higher sensitization of a resist composition,methods have been taken such as use of a low-molecular weight resin,decreasing of the amount of a radiation sensitive material to be added,addition of a material having high dissolution rate in an alkalisolution, and use of a radiation sensitive material having highsensitivity. Of these methods, however, by using a low-molecular-weightresin or decreasing of the amount of a radiation sensitive material tobe added, there arise some problems. That is, though the coatingproperties of the resist composition and the line-width uniformity ofthe resist patterns can be improved, the heat resistance of the resistobtained lowers. As the result, the etching resistance of the resistdrops in the production of semiconductor devices and the like. Further,the developability of the resist composition becomes so poor that scum(residue in development) is formed and the film retention rate drops.For example, when the amount of the radiation sensitive material is lessthan conventional, for example 20 parts by weight or less relative to100 parts by weight of the resin, the film retention properties of theresist composition containing only novolak resin as the resin componentbecome very poor. The composition does not function as a resist. By wayof example, the amount of the radiation sensitive material to be usedconventionally is about 25 parts by weight relative to 100 parts byweight of the resin component in the radiation sensitive composition.

To solve above-described problems, the techniques have been proposed inwhich two or more kinds of novolak resins derived from specific phenolcompounds and having a specified molecular weight range are used as thenovolak resin (Japanese Unexamined Patent Publication No. H07-271024); anovolak resin derived from a specific phenol compound and having aspecified molecular weight range and degree of dispersion is used as thenovolak resin and further a polyhydroxy compound having phenolichydroxyl groups is used (Japanese Unexamined Patent Publication No.H08-184963); and a radiation sensitive component comprising a mixture ofa naphthoquinonediazide-sulfonic acid ester of trihydroxybenzophenoneand trihydroxybenzophenone in a certain ratio is used (JapaneseUnexamined Patent Publication No. H08-82926).

Further, when the conventional radiation sensitive composition isapplied onto a large glass substrate, there arises the problem that theuniformity of pattern line width on the surface cannot be sufficientlyachieved because of the increase of uneven application or the uneventhickness of the resist film. To improve the coating properties of sucha radiation sensitive composition, the addition of a surfactant to theradiation sensitive composition and the type and amount of thesurfactant to be added have been examined. Further, in the examinationof solvent as improvement of coating properties, use of a solvent havinga specific boiling point, kinematic viscosity and evaporation rate(Japanese Unexamined Patent Publication No. 10-186637) and use of amixed solvent containing as one component therein a solvent selectedfrom propylene glycol and dipropylene glycol (Japanese Unexamined PatentPublication No. 10-186638) are reported.

However, even by these various proposals, there is none of the radiationsensitive composition which can simultaneously and sufficiently solvethe problems of sensitivity, resist layer-remaining properties,resolution, reproducibility of patterns, improvement of throughputduring production, coating properties, process dependency etc. Thereforeit is desired to provide a radiation sensitive composition free of suchproblems, that is, capable of simultaneously and sufficiently solvingthe problems of high sensitivity, highly normalized film remainingcharacteristics, high resolution, excellent reproducibility of patterns,improvement of throughput during production, good coating properties,low process dependency etc. Further, for reducing the costs of theradiation sensitive composition, it is also desired to reduce the amountof a radiation sensitive material to be added which has a high unitcost, but if the amount of the radiation sensitive material to be addedis reduced, there arise the problems described above.

On the other hand, it is known that by mixing two or more resins havingdifferent refractive indexes so as to satisfy specific conditions, thereoccurs the phenomenon of light scattering. For example, JapaneseUnexamined Patent Publication No. H05-249319 shows that a polymerizablemonomer is mixed with polymer solid particles, a monomer or a liquideach having a refractive index different from the polymerizable monomer,and the mixture is polymerized to obtain a light-scattering andlight-piping body which can guide an incident light from a single ormany directions while the light is scattered. As typical applicationexamples using this effect of light scattering, plated wave-guides forback light of liquid crystal displays (for example, Japanese UnexaminedPatent Publication Nos. H06-186560, H07-169311 etc.) can be mentioned.In addition, Japanese Unexamined Patent Publication No. H08-255983discloses a method wherein a radiation sensitive composition insulatorcontaining in a negative-working radiation sensitive composition a lightscattering filler having a refractive index different by 0.1 to 0.7 fromthe negative-working radiation sensitive composition is used, and viaholes tapered by light scattering are formed. However, this does notimprove the sensitivity and development properties of the radiationsensitive composition.

Under the circumstances described above, an object of the presentinvention is to provide a radiation sensitive composition havingsensitivity equal to or higher than in the conventional one and highlynormalized film remaining characteristics even when the amount of aradiation sensitive material contained in the radiation sensitivecomposition is reduced than that in the conventional one.

Another object of the present invention is to provide a radiationsensitive composition which permits highly normalized film remainingcharacteristics and high sensitivity to practically stand together, isexcellent in development properties, and can form excellent patterns.

A further object of the present invention is to provide a radiationsensitive composition which has excellent coating properties, excellentline width uniformity of resist patterns, and low process dependency aswell as satisfies the characteristics described above.

DISCLOSURE OF THE INVENTION

As a result of eager study and examination, the present inventors foundthat in a radiation sensitive composition comprising resins and aradiation sensitive material, the working effect of the radiationsensitive material can be increased using at least two kinds of resinhaving refractive indexes different from each other by 0.03 or more asthe resins, and therefore the amount of the radiation sensitive materialused can be reduced, and also that by incorporating a resin working as adissolution inhibitor into a radiation sensitive composition comprisingan alkali-soluble resin and a quinonediazide radiation sensitive agent,excellent resist patterns can be formed without a reduction in thicknessof resist layer after development even if the amount of the radiationsensitive material to be added is reduced, thus having achieved thepresent invention based on the finding.

That is, in the first aspect of the present invention, the presentinvention relates to a radiation sensitive composition comprising aresin composition and a radiation sensitive material, wherein the resincomposition comprises two or more kinds of resins different inrefractive index, further where the resins have a difference inrefractive index of at least 0.03.

Further, in the second aspect of the present invention, the presentinvention relates to a radiation sensitive composition comprising aresin composition and a radiation sensitive material, wherein the resincomposition comprises at least (a) a resin component of analkali-soluble resin and (b) a resin additive working as a dissolutioninhibitor, and the radiation sensitive material is (c) a radiationsensitive material containing a quinonediazide group.

Hereinafter, the present invention is described in detail.

In the first aspect of the present invention, the radiation sensitivecomposition shall contain at least a pair of resins with a refractiveindex difference (Δn) of 0.03 or more each other as a resin composition.The type and number of the resins used is not limited in the presentinvention. As one of the resins having different refractive indexes andused as a resin component in the resin composition of these radiationsensitive compositions, that is the resin component, there is preferablyillustrated an alkali-soluble resin. When the alkali-soluble resin isused as the resin component in the resin composition, the radiationsensitive composition of the first present invention comprises (a) aresin component comprising an alkali-soluble resin and (b) a resinadditive having a different refractive index of 0.03 or more relative tothat of the resin of the resin component. Further, a novolak resin ispreferably used as the alkali-soluble resin in the first presentinvention.

According to the first present invention, the working effect of theradiation sensitive material is improved using at least a pair of resinswith a refractive index difference (Δn) of 0.03 or more each other asthe resin composition used in the radiation sensitive composition. As aresult, the amount of the radiation sensitive material used in theradiation sensitive composition can be reduced and the improvement ofthroughput can also be achieved by higher sensitization of the radiationsensitive composition.

However, when e.g. an alkali-soluble resin is used as the resincomponent and a quinonediazide radiation sensitive agent is used as theradiation sensitive material in the radiation sensitive compositiondescribed above, resist layer-remaining properties of the radiationsensitive composition may be lowered depending on the resin used as theresin additive in the case where the amount of the radiation sensitiveadditive to be added is lower than conventional. If the resin additivecould work as a dissolution inhibitor for the radiation sensitivecomposition, no deterioration in such resist layer-remaining propertieswas found. The reason is ascribed as follows. In the case of theconventional radiation sensitive composition where only the novolakresin i.e. an alkali-soluble resin is used as the resin component in theradiation sensitive composition, the rate of dissolution of theradiation sensitive composition in an alkali developing solution dependsconsiderably on the weight average molecular weight of the novolak resinand the amount of the radiation sensitive material to be added. Whenthese are regulated to attain higher sensitivity, the developmentproperties and resist layer-remaining properties are deteriorated asdescribed above. However if the novolak resin is used in combinationwith a resin working as a dissolution inhibitor as the resin additive,the highly normalized film remaining characteristics are maintained evenif the amount of the radiation sensitive material relative to thenovolak resin is reduced, and higher sensitivity due to the use of asmall amount of the radiation sensitive material is obtained, thus beingachieved higher sensitization without any deterioration in the resistlayer-remaining properties.

In the second present invention using the resin which works as adissolution inhibitor, sensitivity can be improved by reducing theamount of the radiation sensitive material to be added, and thus it isnot always necessary to use a resin as the resin additive having arefractive index different by 0.03 or more from the refractive index ofthe resin component. However, if the refractive index of the resin asthe resin additive is different by 0.03 or more from the refractiveindex of the resin as the resin component, the sensitivity of theradiation sensitive composition can thereby be improved so that furthergood results can be obtained from the viewpoint of the reduction of theamount of the radiation sensitive material added. Accordingly, even inthe second aspect of the invention, the refractive index of the resin asthe resin additive is different preferably by 0.03 or more from therefractive index of the alkali-soluble resin.

In the present invention, the “resin working as a dissolution inhibitor”refers to a resin which when added together with the resin as the resincomponent to the radiation sensitive composition, can inhibit the rateof dissolution in developing solution of the radiation sensitivecomposition film in non-exposed portion thereof, as compared with thecase where the resin is not added.

As the resin working as a dissolution inhibitor, a resin showing a rateof dissolution of 5000 Å/min. or less in 2.38 weight-% aqueous solutionof tetramethyl ammonium hydroxide is preferable when added to theradiation sensitive composition.

Moreover, it is necessary that the respective resins used in theradiation sensitive composition of the present invention can bedissolved in the same solvent even if there is a difference insolubility among them.

The reason that the working effect of the radiation sensitive materialin the radiation sensitive composition can be improved by use of two ormore resins having different refractive indexes is not sufficientlyelucidated but considered to be as follows. However, the following isnot intended to limit the present invention.

That is, in the present invention, the radiation sensitive compositioncomprising two or more resins having different refractive indexes isapplied to form a photoresist film. The present inventors confirmed thateven if a film is formed from a solution prepared by dissolving in asolvent two or more resins having different refractive indexes, the filmthus formed has a heterogeneous structure at the micron level, which isirradiated with light to bring about the phenomenon of light scattering.This phenomenon can also be confirmed by irradiation of the resinsolution with laser light. For example, when a solution with a singlecomposition of a novolak resin or a polymethyl methacrylate resin isirradiated with laser light, the laser light advances withoutscattering. However when a resin solution consisting of a mixture of anovolak resin and, for example, polymethyl methacrylate having arefractive index different from that of the novolak resin is irradiatedwith laser light, the phenomenon of light scattering can be confirmed ina light entering portion.

The reason that a film formed by applying a solution of two or moreresins having different refractive indexes each other in solvent stillpossesses a micro-heterogeneous structure is considered due to thedifference of the solubility of each resin in the solvent. That is, theresin solution is applied to form a coating layer, and then the solventis evaporated from the coating layer by baking. On the baking the resinhaving a lower solubility in the solvent is first precipitated to formsolids, and thereafter the resin having a higher solubility in thesolvent is precipitated to form a micro-heterogeneous structure, thusproviding conditions for light scattering.

When the film formed from the radiation sensitive composition containingtwo or more resins having different refractive indexes is irradiatedwith light, the phenomenon of light scattering in the film occurs owingto the factor described above. When the film is exposed, the incidentlight is repeatedly scattered in the film thus providing a very longlight path to improve the efficiency of utilization of irradiation lightsignificantly, as compared with the light path in a film formed from theconventional radiation sensitive composition showing none of thephenomenon of light scattering. While the conventional radiationsensitive composition is poor in the efficiency of utilization ofirradiation light because irradiation light is reflected and losttowards the outside of the radiation sensitive resin film, the radiationsensitive composition of the present invention achieves a very highefficiency of utilization of irradiation light because the distance ofincident light transmitted is made longer by the effect of lightscattering, whereby the working effect on the radiation sensitivematerial is significantly improved and higher sensitivity can beachieved.

Hereinafter, the resin component, the resin additive, and anothercomponents of the radiation sensitive composition in the presentinvention will be described below respectively in more detail.

Resin Component

As a resin of the resin component composing the resist composition inthe radiation sensitive composition of the present invention, any resinsused as resin components in the conventional radiation sensitivecomposition can be used. Among the resin components used in theconventional radiation sensitive composition, an alkali-soluble resin ispreferable as the resin component of the present invention.

The alkali-soluble resin used in the radiation sensitive composition ofthe present invention may be any alkali-soluble resin used in theconventional radiation sensitive composition known in the art. As thealkali-soluble resin, novolak resin is preferable, but this does notparticularly limit the present invention.

An alkali-soluble novolak resin preferably used in the present inventionis obtainable by a polycondensation between one kind of phenols or amixture thereof and at least one kind of aldehydes such as formalin.

As the phenols to be used for preparing the novolak resin, there may beillustrated, for example, phenol, p-cresol, m-cresol, o-cresol,2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol,2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol,2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol,2,4,5-trimethylphenol, methylene-bisphenol, methylene-bisp-cresol,resorcinol, catechol, 2-methylresorcinol, 4-methylresorcinol,o-chlorophenol, m-chlorophenol, p-chlorophenol, 2,3-dichlorophenol,m-methoxyphenol, p-methoxyphenol, o-methoxyphenol, p-butoxyphenol,o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-diethylphenol,2,5-diethylphenol, p-isopropylphenol, α-naphthol, β-naphthol, and thelike. These are used independently or as a mixture of two or morethereof.

As the aldehydes, there may be illustrated paraformaldehyde,acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde,etc. as well as formalin. These are used singly or as a mixture of twoor more thereof.

The weight average molecular weight of the novolak resin used in theradiation sensitive composition of the present invention, as determinedusing polystyrene standards, is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 3,000 to 15,000.

Resin Additive

The resin as the resin additive composing the resin composition in theradiation sensitive composition of the present invention may be anyresin which has a refractive index different by 0.03 or more from thatof the resin component and/or works as a dissolution inhibitor. Theresin having such characteristics includes polyacrylic ester,polymethacrylic ester, polystyrene derivatives, polyvinyl benzoate,polyvinyl phenyl acetate, polyvinyl acetate, polyvinyl chloroacetate,polyacrylonitrile, poly-α-methylacrylonitrile, polyvinyl phthalimide,and copolymers obtained from two or more monomers selected from acrylicester, methacrylic ester, styrene derivatives, vinyl benzoate, vinylphenyl acetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidazole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone.

Among these resins, the resin as the resin additive in the presentinvention is preferably polyacrylic ester, polymethacrylic ester,polystyrene derivatives, and copolymers obtained from at least two kindsof monomers selected from acrylic esters, methacrylic esters and styrenederivatives. If a repeating unit having a carboxyl group or a carboxylicanhydride group is further contained in these resins, analkali-insoluble portion of the polymer consisting of a repeating unitpart derived from acrylic esters, methacrylic esters, styrenederivatives, etc. shows a dissolution inhibiting effect, while analkali-soluble portion consisting of a repeating unit part having acarboxyl group or a carboxylic anhydride group improves the solubilityof the radiation sensitive composition in a developing solution, wherebythe dissolution inhibiting effect and solubility improvement effect ofthe radiation sensitive composition can be preferably balanced by use ofthe resin additive.

Accordingly, as the resin of the resin additive, copolymers obtainedfrom at least one member selected from acrylic ester, methacrylic esterand styrene derivatives and an organic acid monomer having a carboxylgroup or a carboxylic anhydride group are also a preferable resin.

Examples of polyacrylic ester, polymethacrylic ester and polystyrenederivatives which can be preferably used as the resin of the resinadditive in the present invention are as follows.

Polyacrylic Ester:

Polymethyl acrylate, polyethyl acrylate, poly-n-propyl acrylate,poly-n-butyl acrylate, poly-n-hexyl acrylate, polyisopropyl acrylate,polyisobutyl acrylate, poly-t-butyl acrylate, polycyclohexyl acrylate,polybenzyl acrylate, poly-2-chloroethyl acrylate,polymethyl-α-chloroacrylate, polyphenyl α-bromoacrylate etc.

Polymethacrylic Ester:

Polymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate,polyphenyl methacrylate, poly-l-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate etc.

Polystyrene Derivatives:

Poly-4-fluorostyrene, poly-2,5-difluorostyrene,poly-2,4-difluorostyrene. poly-p-isopropylstyrene, polystyrene,poly-o-chlorostyrene, poly-4-acetylstyrene, poly-4-bezoylstyrene,poly-4-bromostyrene, poly-4-butoxycarbonylstyrene,poly-4-butoxymethylstyrene, poly-4-butylstyrene, poly-4-ethylstyrene,poly-4-hexylstyrene, poly-4-methoxystyrene, poly-4-methylstyrene,poly-2,4-dimethylstyrene, poly-2,5-dimethylstyrene,poly-2,4,5-trimethylstyrene, poly-4-phenylstyrene,poly-4-propoxystyrene, polyaminostyrene etc.

As monomers preferably used for preparing a copolymer obtained from atleast two monomers selected from acrylic ester, methacrylic ester, andstyrene derivatives or a copolymer obtained from at least one of thesemonomers and an organic acid monomer having a carboxyl group or acarboxylic anhydride group, there are illustrated monomers used forpreparing above described polyacrylic ester, polymethacrylic ester andpolystyrene derivative with regard to acrylic ester, methacrylic esterand styrene derivatives. As organic acid monomers having a carboxylgroup or a carboxylic anhydride group, there are preferably illustratedas followed.

Organic Acid Monomer Having a Carboxyl Group or a Carboxylic

Anhydride Group:

Acrylic acid, methacrylic acid, itaconic acid, maleic anhydride,2-acryloylhydrogenphthalate, 2-acryloyloxypropyl hydrogenphthalate etc.

The copolymer containing an acid component in repeating units, usedpreferably in the present invention, can be produced in a usual mannerby copolymerizing at least one kind of monomer selected from monomerssuch as the acrylic esters, methacrylic esters and styrene derivativesdescribed above with at least one kind of monomer selected from theorganic acid monomers described above. As acrylic copolymers among thesecopolymers there are preferably illustrated copolymers between one kindof monomer selected from the acrylic esters and methacrylic estersdescribed above and at least one kind of organic acid monomer selectedfrom the organic acid monomers described above, and copolymers betweentwo kinds of monomers selected from the acrylic esters and methacrylicesters described above and at least one kind of organic acid monomerselected from the organic acid monomers described above, and morepreferably copolymers between methyl methacrylate, at least one kind ofmethacrylic ester excluding methyl methacrylate, and at least one memberselected from acrylic acid and methacrylic acid.

When the acid value of polyacrylic ester- or polymethacrylic ester-basedresin and polystyrene derivative-based resin made of a copolymerobtained from at least one kind of monomer selected from the acrylicesters, methacrylic esters and styrene derivatives and an organic acidmonomer having a carboxyl group or a carboxylic anhydride group is 1 to80 mg KOH/g, the good coating properties of the radiation sensitivecomposition can be preferably obtained. It was also found that the resinhaving an acid value of 1 to 80 mg KOH/g can be used as the resin of theresin additive to achieve excellent line width uniformity with lowprocess dependency of resist patterns. The acid value of the polyacrylicester- or polymethacrylic ester-based resin or polystyrenederivative-based resin is more preferably 2 to 30 mg KOH/g.

When the organic acid monomer is used as a copolymerizable component inthe copolymer, the amount of the organic acid monomer used is preferably0.1 to 10.0 parts by weight, more preferably 0.5 to 3.0 parts by weight,relative to 100 parts by weight of the other monomer components.

The copolymer containing the acid component described above is notlimited to a product obtained by copolymerizing monomers correspondingto repeating units constituting the copolymer described above. Thecopolymer containing the acid component may be one prepared by anarbitrary method such as a method of introducing an acid component intoa polymer, for example by hydrolyzing a polymer having at least one kindof acrylic ester and methacrylic ester polymerized therein.

The weight average molecular weight of the resin as the resin additive,as determined using polystyrene standards, is preferably 2,000 to80,000. When the resin contains styrenic monomer-repeating units of lessthan 50 mole-% of repeating units in the resin, such as polyacrylic acidester- or polymethacrylic acid ester-based resin, the weight averagemolecular weight of the resin as determined using polystyrene standards,is more preferably 5,000 to 40,000 and most preferably 7,000 to 20,000.When the resin contains styrenic monomer-repeating units of not lessthan 50 mole-% of repeating units in the resin, such as polystyrenederivatives, the weight average molecular weight of the resin is morepreferably 3,000 to 25,000 and most preferably 5,000 to 20,000.

Such resins consisting of homopolymers or copolymers may be used singlyor in combination thereof as the resin additive.

The refractive indexes of some of the above-exemplified resins as theresin additive are shown below. The refractive index of the novolakresin used preferably as the resin component is 1.64 as determined at awavelength of 436 nm (hereinafter, reflective index at a wavelength of436 nm is shown).

Resins Having a Refractive Index of Less Than 1.50:

Polymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polymethyl acrylate, polyethyl acrylate, poly-n-butylacrylate and polyvinyl acetate etc.

Resins Having a Refractive Index of 1.50 to 1.60:

Polycyclohexyl methacrylate, polybenzyl methacrylate, polyphenylmethacrylate, poly-1-phenylethyl methacrylate, poly-2-phenylethylmethacrylate, polyfurfuryl methacrylate, polybenzyl acrylate,poly-2-chloroethyl acrylate, polyvinyl benzoate, polyvinylphenylacetate, polyvinyl chlorocetate, polyacrylonitrile,poly-α-methylacrylonitrile, polymethyl-α-chloroacrylate,poly-p-fluorostyrene, poly-o,p-fluorostyrene, poly-p-isopropylstyrene,polystyrene and polydiphenylmethyl methacrylate etc.

Resins Having a Refractive Index of More Than 1.60:

Polyphenyl-α-bromoacrylate, polynaphthyl methacrylate,polyvinylphthalimide and poly-o-chlorostyrene, polypentachlorophenylmethacrylate etc.

As the resin of the resin additive used together with the novolak resin,polymers of methacrylic esters such as polymethyl methacrylate,polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butylmethacrylate, poly-n-hexyl methacrylate, polyisopropyl methacrylate,polyisobutyl methacrylate, poly-t-butyl methacrylate, polydiphenylmethylmethacrylate, polypentachlorophenyl methacrylate etc., polymers ofpolystyrene derivatives such as polystyrene or copolymers obtainedusing, as at least one of copolymer components, monomer(s) used forproducing these polymers are particularly preferable resins.

Because the proportion of the amount of the resin additive to the amountof the resin component is varied depending on the type of resin used asthe resin component and the resin additive, it is difficult to define agenerally preferable range thereof. By way of example, in a combinationof novolak resin of the alkali-soluble resin and a resin of resinadditive such as a homopolymer or copolymer of methacrylic estercontaining styrene derivative-repeating units, that is styrenicmonomer-repeating units of less than 50 mole-% of repeating units in theresin, the amount of the resin additive is preferably 1 to 20 parts byweight, more preferably 1 to 15 parts by weight, relative to 100 partsby weight of novolak resin. When the resin additive is a styrenic resinhaving styrenic monomer-repeating units of not less than 50 mole-% ofrepeating units in the resin, the amount of the styrenic resin ispreferably 0.5 to 5.0 parts by weight, more preferably 1.0 to 3.0 partsby weight, relative to 100 parts by weight of the novolak resin.

Other Resin Components Than the Resin Component and Resin Additives

In the resin composition used in the radiation sensitive composition ofthe present invention, for balancing the dissolution inhibiting effectwith the solubility improvement of the radiation sensitive composition,a polymer having carboxyl group or a carboxylic anhydridegroup-repeating units of 50 mole-% or more of repeating units in theresin can be further contained in addition to the resin componentconsisting of the alkali-soluble resins and the resin additive describedabove. The proportion of such a homopolymer of the organic acid monomeror a copolymer containing the organic acid monomer as a major componentof the copolymer to the resin additive is preferably 0.1 to 10.0 partsby weight, more preferably 0.5 to 3.0 parts by weight, relative to 100parts by weight of the resin additive. The amount of such resincomponents other than the resin component and the resin additive, interms of the total amount thereof with the resin additive, is 1 to 20parts by weight, more preferably 1 to 10 parts by weight and mostpreferably 2 to 5 parts by weight, relative to 100 parts by weight ofthe novolak resin.

The polymers containing repeating-units having a carboxyl group or acarboxylic anhydride group of 50 mole-% or more of repeating units to bepreferably used in this invention are as follows.

Polymers Containing Organic Acid Monomers of 50 mole-% or More ofMonomer Components:

Polyacrylic acid, polymethacrylic acid, polyitaconic acid, polymaleicanhydride, poly-2-acryloyl hydrogenphthalate, andpoly-2-acryloyloxypropyl hydrogenphthalate, as well as copolymersprepared using 50 mole-% or more of monomers used for preparing thesepolymers as a monomer component.

Further, it is more preferable that the radiation sensitive compositionof the present invention, wherein the value of X which is B/A is in therange of 0.01 to 0.13 whereupon A is an integrated area beneath peaks inthe range of 7.2 to 5.6 ppm and B is an integrated area beneath peaks inthe range of 1.3 to 0.95 ppm in a ¹H-NMR spectrum of a solution of theresin components in heavy acetone.

In the present invention, the integrated value A of peaks in the rangeof 7.2 to 5.6 ppm and the integrated value B of peaks in the range of1.3 to 0.95 ppm in a ¹H-NMR spectrum of a solution of the resincomposition in heavy acetone are found by integrating areas beneathpeaks in the range of 7.2 to 5.6 ppm or 1.3 to 0.95 ppm in NMR spectrumof the resin composition measured in the following manner, and thevalues thus obtained are used to calculate X=B/A.

First, the alkali-soluble resin is dissolved in propylene glycolmonomethyl ether acetate, and this solution is spin-coated on asubstrate to form a film thereon. This film is dissolved in heavyacetone to prepare a NMR spectrum measurement sample, and measurement ofits ¹H-NMR spectrum is conducted using the sample, and on the basis ofthe resulting chart, the integrated value of peaks in the range of 7.2to 5.6 ppm is calculated as A, and the integrated value of peaks in therange of 1.3 to 0.95 ppm excluding a peak of propylene glycol monomethylether acetate as the solvent is calculated as B, to calculate B/A togive X.

Radiation Sensitive Material

The radiation sensitive material used in the radiation sensitivecomposition of the present invention may be any radiation sensitivematerial used in the conventional radiation sensitive compositioncomprising a resin component and a radiation sensitive material.

In the radiation sensitive composition of the present invention, whenthe alkali-soluble resin is used as the resin component of the resincomposition, a radiation sensitive material containing a quinonediazidegroup or groups is preferable as the radiation sensitive material.

The radiation sensitive materials having a quinonediazide group orgroups used in the present invention may be any one of theconventionally known radiation sensitive materials having quinonediazidegroup or groups. Preferred examples of the radiation sensitive materialshaving quinonediazide group or groups include a compound obtainable fromthe reaction between a naphthoquinonediazidesulfonic acid halide such as1,2-naphthoquinonediazide-4-sulfonyl chloride and1,2-naphthoquinonediazide-5-sulfonyl chloride or quinonediazidesulfonicacid halide such as benzoquinonediazidesulfonic acid chloride, and a lowmolecular compound or a high molecular compound having a functionalgroup capable of reacting with the acid halide by condensation. Examplesof the functional group capable of condensing with the acid halideinclude a hydroxyl group, an amino group, and so on. Among these groups,a hydroxyl group is particularly suitable.

Examples of the above-described low molecular compound containinghydroxyl group or groups include hydroquinone, resorcinol,2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone,2,4,6-trihydroxybenzophenone, 2,4,4′-trihydroxybenzophenone,2,3,4,4′-tetrahydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophenone,2,2′,3,4,6′-pentahydroxybenzophenone etc. Examples of the high molecularcompound containing hydroxyl group include novolak resin andpolyhydroxystyrene etc.

From the viewpoint of use of a lower amount of the radiation sensitivematerial, when the resin of the resin additive consist of one containingstyrenic monomer-repeating units or less than 50 mole-% of repeatingunits in the resin, the radiation sensitive material containingquinonediazide group or groups is used preferably in an amount of 1 to20 parts by weight relative to 100 parts by weight of the alkali-solubleresin in the radiation sensitive composition of the present invention.Further, when the resins working as a dissolution inhibitor are used asthe resin additive, from the viewpoint of the coating properties of theradiation sensitive composition, the amount of the radiation sensitivematerial containing quinonediazide group or groups is often moredesirably 1 to 18 parts by weight relative to 100 parts by weight of thealkali-soluble resin in the radiation sensitive composition.Additionally, when the resin containing styrenic monomer-repeating unitsof 50 mole-% of repeating units in the resin is used as the resinadditive, the amount of the radiation sensitive material containingquinonediazide group are preferably 10 to 30 parts by weight, morepreferably 15 to 25 parts by weight relative to 100 parts by weight ofthe alkali-soluble resin in the radiation sensitive composition. If thecontents of the radiation sensitive material are less than 10 parts byweight, the resist layer-remaining rate of the radiation sensitivecomposition tends to lower. Further, if the contents of the radiationsensitive material are more than 30 parts by weight, it is notpractically as the sensitivity of the radiation sensitive composition istoo low.

Additives

In addition, a low-molecular compound represented by the general formula(I) below and having phenolic hydroxyl group or groups can be added inthe radiation sensitive composition of the present invention.

Wherein R₁, R₂, R₃, R₄, R₅, R₆ and R₇ each represents independently H, aC₁ to C₄ alkyl group, a C₁ to C₄ alkoxyl group, a cyclohexyl group or agroup represented by the formula:

wherein R₈ represents H, a C₁ to C₄ alkyl group, a C₁ to C₄ alkoxylgroup or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b,c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5,c+d≦5, e+f≦5, and g+h≦5; and i is 0, 1 or 2.

The low-molecular compound having phenolic hydroxyl group or groupsrepresented by the above general formula (I) is preferably used as adissolution accelerator usually for regulating dissolution rate of theradiation sensitive composition of the present invention, or improvingor regulating the sensitivity of the radiation sensitive composition.

As the low-molecular compound having phenolic hydroxyl group or groupsrepresented by the above general formula (I), there are illustrated, forexample, o-cresol, m-cresol, p-cresol, 2,4-xylenol, 2,5-xylenol,2,6-xylenol, bisphenol A. B, C, E, F, or G,4,4′,4″-methylidinetrisphenol,2,6-bis[(2-hydroxy-5-methylphenol)methyl]-4-methylphenol,4,4′-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol,4,4′,4″-ethylidinetrisphenol,4-[bis(4-hydroxyphenyl)methyl]-2-ethoxyphenol,4,4′-[(2-hydroxyphenyl)methylenelbis[2,3-dimethylphenol],4,4′-[(3-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],4,4′-[(4-hydroxyphenyl)methylene]bis[2,6-dimethylphenol],2,2′-[(2-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],2,2′-[(4-hydroxyphenyl)methylene]bis[3,5-dimethylphenol],4,4′-[(3,4-dihydroxyphenyl)methylene]bis[2,3,6-trimethylphenol],4-[bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)methyl]-1,2-benzenediol,4,6-bis[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,2,3-benzenetriol,4,4′-[(2-hydroxyphenyl)methylene]bis[3-methylphenol],4,4′,4″-(3-methyl-1-propanyl-3-ylidine)trisphenol,4,4′,4″,4′″-(1,4-phenylenedimethylidine)tetrakisphenol,2,4,6-tris[(3,5-dimethyl-4-hydroxyphenyl)methyl]-1,3-benzenediol,2,4,6-tris[(3,5-dimethyl-2-hydroxyphenyl)methyl]-1,3-benzenediol,4,4′-[1-[4-[1-[4-hydroxy-3,5-bis[(hydroxy-3-methylphenyl]methyl]phenyl]-1-methylethyl]phenyl]ethylidene]bis[2,6-bis(hydroxy-3-methylphenyl)methyl]phenol,and the like. These low-molecular compounds having phenolic hydroxylgroup or groups are used in an amount of usually 1 to 20 parts byweight, preferably 3 to 15 parts by weight relative to 100 parts byweight of the novolak resin.

Further, dyestuffs, adhesive aids, surfactants etc. may be incorporatedas necessary into the radiation sensitive composition of the presentinvention. The dyestuffs include e.g. Methyl Violet, Crystal Violet,Malachite Green etc.; the adhesive aids include e.g. alkyl imidazoline,butyric acid, alkyl acid, polyhydroxystyrene, polyvinylmethyl ether,t-butyl novolak, epoxy silane, epoxy polymer, silane etc.; and thesurfactants include e.g. nonionic surfactants such as polyglycols andderivatives thereof, that is, polypropylene glycol or polyoxyethylenelauryl ether, fluorine-containing surfactants such as Fluorad (tradename; manufactured by Sumitomo 3M Ltd.), Megafac (trade name;manufactured by Dainippon Ink & Chemicals, Inc.), Sulflon (trade name;manufactured by Asahi Glass Co., Ltd.) or organosiloxane surface activeagents such as KP341 (trade name; Shin-Etsu Chemical Co., Ltd.).

Solvent

The examples of solvents for dissolving the resin component of the resincomposition, the radiation sensitive material, other additives etc.contained in the radiation sensitive composition of the presentinvention include ethylene glycol monoalkyl ethers such as ethyleneglycol monomethyl ether and ethylene glycol monoethyl ether; ethyleneglycol monoalkyl ether acetates such as ethylene glycol monomethyl etheracetate and ethylene glycol monoethyl ether acetate; propylene glycolmonoalkyl ethers such as propylene glycol monomethyl ether and propyleneglycol monoethyl ether; propylene glycol monoalkyl ether acetates suchas propylene glycol monomethyl ether acetate and propylene glycolmonoethyl ether acetate; lactates such as methyl lactate and ethyllactate; aromatic hydrocarbons such as toluene and xylene; ketones suchas methyl ethyl ketone, 2-heptanone, and cyclohexanone; amides such asN,N-dimethylacetamide and N-methylpyrrolidone; lactones such asγ-butyrolactone; and so on. These solvents are used singly or in acombination of two or more thereof.

In the present invention, the rates of dissolution of the radiationsensitive composition in 2.38 weight-% aqueous solution of tetramethylammonium hydroxide are measured and calculated in the following manner.

(Method of Measuring the Rate of Dissolution of the Radiation SensitiveComposition)

The radiation sensitive composition was spin-coated on a silicon waferand baked at 100° C. for 90 seconds on a hot plate to give a photoresistfilm of about 1.5 μm in thickness. The thickness d₁ (Å) of thephotoresist film at this time was measured, and this resist film wasexposed through a test pattern with line and space patterns havingvarious line and space widths and a line-to-space width ratio of 1:1,using an FX-604F stepper manufactured by Nikon Co. Thereafter, it wasdeveloped at 23° C. for 60 seconds with 2.38 weight-% aqueous solutionof tetramethyl ammonium hydroxide. After development, the thickness d₂(Å) of the photoresist film was measured again, and the rate ofdissolution (Å/min.) was determined from the difference (d₁-d₂) in thethickness of the film before and after development.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H-NMR spectrum chart of a resin composition obtained bymeasuring a film of a mixed resin consisting of a novolak resin and anacrylic polymer (100:10) as a sample.

FIG. 2 is a ¹H-NMR spectrum chart of a radiation sensitive compositionobtained by measuring a resist film formed from a radiation sensitivecomposition prepared using as the resin composition the mixed resinconsisting of a novolak resin and an acrylic polymer (100:10) as asample.

BEST MODE FOR PRACTICING THE INVENTION

The present invention will now be described more specifically byreference to Examples, Comparative Examples and Synthesis Exampleswhich, however, are not to be construed to limit the present inventionin any way. Additionally, in the following Examples, “molecular weight”or “weight average molecular weightn” means “weight average molecularweight as determined using polystyrene standards” unless otherwisespecified.

SYNTHESIS EXAMPLE Synthesis Example 1

900 g of propylene glycol monomethyl ether acetate, 189 g of methylmethacrylate, 81 g of t-butyl methacrylate, 30 g of acrylic acid, 6 g ofazobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrile werecharged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 15,000 in weight averagemolecular weight and 80 mg KOH/g in acid value.

Synthesis Example 2

900 g of propylene glycol monomethyl ether acetate, 207.9 g of methylmethacrylate, 89.1 g of t-butyl methacrylate, 3 g of acrylic acid, 6 gof azobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrilewere charged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 13,000 in weight averagemolecular weight and 8 mg KOH/g in acid value.

Synthesis Example 3

900 g of propylene glycol monomethyl ether acetate, 207.9 g of methylmethacrylate, 89.1 g of n-butyl methacrylate, 3 g of acrylic acid, 6 gof azobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrilewere charged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 13,000 in weight averagemolecular weight and 8 mg KOH/g in acid value.

Synthesis Example 4

900 g of propylene glycol monomethyl ether acetate, 207.9 g of methylmethacrylate, 89.1 g of cyclohexyl methacrylate, 3 g of acrylic acid, 6g of azobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrilewere charged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 12,000 in weight averagemolecular weight and 8 mg KOH/g in acid value.

Synthesis Example 5

900 g of propylene glycol monomethyl ether acetate, 210 g of methylmethacrylate, 90 g of t-butyl methacrylate, 0.3 g in of acrylic acid, 6g of azobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrilewere charged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 13,000 in weight averagemolecular weight and 1 mg KOH/g in acid value.

Synthesis Example 6

900 g of propylene glycol monomethyl ether acetate, 210 g of methylmethacrylate, 90 g of t-butyl methacrylate, 6 g ofazobisdimethylvaleronitrile and 4.5 g of azobismethylbutyronitrile werecharged into a 2000-ml four-necked flask equipped with a stirrer, acooling tube, a thermometer and a nitrogen-introducing tube, andstirred. Then, the temperature of the contents was raised while blowingnitrogen thereinto, and polymerization was conducted at 85° C. for 8hours to obtain an acrylic copolymer of 13,000 in weight averagemolecular weight and 0.3 mg KOH/g in acid value.

EXAMPLE AND COMPARATIVE EXAMPLE Example 1

To 100 parts by weight of a novolak resin (refractive index at 436 nm:1.64) were added 15 parts by weight of an esterification product between2,3,4,4′-tetrahydroxy-benzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride (as a radiation sensitivematerial) and 5 parts by weight of polymethyl methacrylate (PMMA;refractive index at 436 nm: 1.48) having a refractive index differentfrom that of the novolak resin by 0.03 or more and working as adissolution inhibitor, and the resulting mixture was dissolved inpropylene glycol monomethyl ether acetate. After adding thereto 300 ppmof a fluorine-containing surfactant of Fluorad-472 (manufactured bySumitomo 3M Co.) for the purpose of preventing formation of radialwrinkles, so-called striation, to be formed on a resist layer upon spincoating, the solution was stirred and filtered through a 0.2-μm filterto prepare a radiation sensitive composition of the present invention.This composition was spin-coated on a 4-inch silicon wafer, and baked ona hot plate at 100° C. for 90 seconds to obtain a 1.5-μm thick resistlayer. This resist layer was exposed by a g-line stepper made by GCA Co.(DSW 6400) through a test pattern with line and space patterns havingvarious line and space widths and a line-to-space width ratio of 1:1,and developed in a 2.20 weight-% aqueous solution of tetramethylammoniumhydroxide at 23° C. for 60 seconds. After completion of the development,thickness of the layer was again measured. Resist layer-remaining ratiowas determined according to the following formula:

Resist layer-remaining ratio=[(thickness before development−thicknessafter development)/thickness before development]×100

In addition, an amount of exposure energy enough to resolve a a 5-μmline-and-space pattern to 1:1 is determined by observation, which wastaken as a sensitivity. Thus, there were obtained the results shown inTable 1.

Examples 2 and 3 and Comparative Example 1

Procedures were conducted in the same manner as in Example 1 except forchanging the amount of added PMMA as shown in Table 1 relative to 100parts by weight of novolak resin. Thus, there were obtained the resultsshown in Table 1.

Example 4

Procedures were conducted in the same manner as in Example 1 except foradding 10 parts by weight of poly-n-butyl methacrylate (PnBMA;refractive index at 436nm: 1.47) in place of PMMA relative to 100 partsby weight of novolak resin. Thus, there were obtained the results shownin Table 1.

Example 5

Procedures were conducted in the same manner as in Example 1 except foradding 5 parts by weight of PMMA and 5 parts by weight of PnBMA in placeof PMMA relative to 100 parts by weight of novolak resin. Thus, therewere obtained the results shown in Table 1.

Example 6

Procedures were conducted in the same manner as in Example 1 except foradding 10 parts by weight of poly(methyl methacrylate-co-n-butylmethacrylate) [P(MMA-nBMA); refractive index at 436 nm: 1.48] in placeof PMMA relative to 100 parts by weight of novolak resin. Thus, therewere obtained the results shown in Table 1.

Example 7

Procedures were conducted in the same manner as in Example 1 except foradding 10 parts by weight of poly(methyl methacrylate-co-styrene)[P(MMA-St); refractive index at 436 nm: 1.52) in place of PMMA relativeto 100 parts by weight of novolak resin. Thus, there were obtained theresults shown in Table 1.

Example 8

Procedures were conducted in the same manner as in Example 1 except foradding 10 parts by weight of poly-diphenylmethyl methacrylate (PDPMMA;refractive index at 436 nm: 1.59) in place of PMMA relative to 100 partsby weight of novolak resin. Thus, there were obtained the results shownin Table 1.

Example 9

Procedures were conducted in the same manner as in Example 1 except foradding 10 parts by weight of poly-pentachlorophenyl methacrylate(PPCPMA; refractive index at 436 nm: 1.61) in place of PMMA relative to100 parts by weight of novolak resin. Thus, there were obtained theresults shown in Table 1.

Comparative Example 1

Procedures were conducted in the same manner as in Example 1 except fornot using PMMA to obtain results shown in Table 1.

TABLE 1 Amount of added resin additive Resist relative to 100 layer-Resin additive parts by weight of remaining Sensi- added to novolakresin ratio tivity novolak resin (parts by weight) (%) (mJ/cm²) Example1 PMMA  5 100 30 Example 2 PMMA 10 100 25 Example 3 PMMA 15 100 35Example 4 PnBMA 10 100 26 Example 5 PMMA/PnBMA 5/5 100 25 Example 6P(MMA-nBMA) 10 100 25 Example 7 P(MMA-St) 10 100 21 Example 8 PDPMMA 10100 29 Example 9 PPCPMA 10 100 30 Com- —  0 100 50 parative Example 1

Additionally, resist patterns obtained in Examples 1 to 9 had a goodpattern form with no scum.

Example 10

The radiation sensitive composition prepared in Example 1 wasspin-coated on a glass substrate, and baked on a hot plate at 100° C.for 90 seconds to form a 1.2-μm thick resist layer. UV rays-visiblelight absorption spectrum of this resist layer was measured by means ofa spectrophotometer (Cary 4E made by Barian Co.) for UV rays and visiblelight, and the layer was exposed by a g-line stepper, DSW6400 made byGCA Co., in an energy amount of 80 mJ/cm², followed by again measuringUV ray-visible light absorption spectrum. Decomposition ratio of theradiation sensitive material was determined from the change inabsorbance before and after the exposure at 436 nm, wavelength of g-lineaccording to the following formula:

Decomposition ratio=[(absorbance before exposure−absorbance afterexposure)/absorbance before exposure]×100

Examples 11 and 12 and Comparative Example 2

Procedures were conducted in the same manner as in Example 10 except forchanging the amount of added PMMA relative to 100 parts by weight ofnovolak resin as shown in Table 2 to obtain the results tabulated inTable 2.

TABLE 2 Amount of added PMMA Decomposition ratio relative to 100 partsby of a radiation weight of novolak resin sensitive material (parts byweight) (% at 436 nm) Example 10  5 48 Example 11 10 51 Example 12 15 46Comparative  0 39 Example 2

It is seen from the above-described results of Examples 1 to 12 andComparative Examples 1 to 2 that use of at least two kinds of resinsdifferent from each other by 0.03 or more in refractive index as resinsin a resin composition to be used in a radiation sensitive compositionenables one to obtain a radiation sensitive composition having highsensitivity, excellent developability and excellent resistlayer-remaining property. It is also seen that improvement ofsensitivity is attained by the improvement of decomposition ratio ofradiation sensitive materials, i.e., improvement of the working effectof the radiation sensitive materials.

Example 13

100 parts by weight of novolak resin having a weight average molecularweight of 15,000, 15 parts by weight of an esterification productbetween 2,3,4,4′-tetrahydroxy-benzophenone and1,2-naphthoauinonediazide-5-sulfonyl chloride and 4.0 parts by weight ofpoly-t-butyl methacrylate having a weight average molecular weight of18,000 were dissolved in propylene glycol monomethyl ether acetate and,for preventing formation of radial wrinkles, so-called striation, on aresist layer upon spin coating, 300 ppm of a fluorine-containingsurfactant, Fluorad-472 (manufactured by Sumitomo 3M Co.) was addedthereto. After stirring the mixture, it was filtered through a 0.2-μmfilter to prepare a radiation sensitive composition of the presentinvention. Sensitivity and coating properties of the composition weremeasured in the following manner. Results thus obtainedare tabulated inTable 3.

Sensitivity

A radiation sensitive composition to be tested is spin-coated on a4-inch silicon wafer, and baked on a hot plate at 100° C. for 90 secondsto form a 1.5-μm thick resist layer. This resist layer is exposed withvarious exposure energies by a g-line stepper made by Nikon Co.(FX-604F) through a test pattern with line and space patterns havingvarious line and space widths and a line-to-space width ratio of 1:1,and developed in a 2.38 weight-% aqueous solution of tetramethylammoniumhydroxide at 23° C. for 60 seconds. An energy amount enough to resolve a5-μm line-and-space pattern to 1:1 is determined by observation, whichwas taken as a sensitivity.

Coating Properties

A radiation sensitive composition to be tested is spin-coated on achromium layered glass substrate (360 mm×465 mm), and baked on a hotplate at 100° C. for 90 seconds to form a 1.5-μm thick resist layer.Then, thickness of the layer is measured at 600 points of the layer todetermine maximum difference in layer thickness (r) and standarddeviation (σ). Thus, coating properties (uniformity of layer thickness)are confirmed.

Example 14

Procedures were conducted in the same manner as in Example 13 except forchanging the amount of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride to 20 parts by weight toprepare a radiation sensitive composition. Sensitivity and coatingproperties of this radiation sensitive composition were measured in thesame manner as in Example 13. Results thus obtained are tabulated inTable 3.

Comparative Example 3

Procedures were conducted in the same manner as in Example 13 except forchanging the amount of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride to 25 parts by weight andnot adding poly-t-butyl methacrylate to prepare a radiation sensitivecomposition. Sensitivity and coating properties of this radiationsensitive composition were measured in the same manner as in Example 13.Results thus obtained are shown in Table 3.

TABLE 3 Sensitivity Coating properties (mJ/cm²) r (Å) σ (Å) Example 1340 355 50 Example 14 80 490 80 Comparative 80 620 100  Example 3

Resist layer-remaining ratios of the radiation sensitive composition ofExamples 13 and 14 and Comparative Example 3 were 94.0%, 99.0% and 93.5%respectively. It is seen from the results of Examples 13 and 14 andComparative Examples 3 that even when the amount of the radiationsensitive material was reduced, the radiation sensitive composition ofthe present invention had high sensitivity and good resistlayer-remaining property, and showed excellent coating properties.

Example 15

100 parts by weight of a mixture of novolak resin having a weightaverage molecular weight of 6,000 and poly-t-butyl methacrylate (PtBMA)having a weight average molecular weight of 10,000 in mixing ratio of100:3 and 19 parts by weight of an esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved inpropylene glycol monomethyl ether acetate and, for preventing formationof radial wrinkles, so-called striation, on a resist layer upon spincoating, 300 ppm of a fluorine-containing surfactant, Fluorad-472(manufactured by Sumitomo 3M Co.) was added thereto. After stirring themixture, it was filtered through a 0.2-μm filter to prepare a radiationsensitive composition of the present invention. Sensitivity and coatingproperties of this radiation sensitive composition were measured in thesame manner as in Example 13. Additionally, in this Example, bakingtemperature upon formation of the resist layer for measuring sensitivitywas 95° C., 100° C., or 105° C., and sensitivity was measured withrespect to resist layers having been baked at respective temperatures.Results thus obtained are tabulated in Tables 4 and 5.

Example 16

Procedures were conducted in the same manner as in Example 15 except forusing novolak resin having a weight average molecular weight of 15,000to obtain results shown in Tables 4 and 5.

TABLE 4 Novolak resin: Amount of PtBMA Molecular a (ratio weight ofradiation Sensitivity S (mJ/cm²) by novolak sensitive ΔS weight) resinmaterial 95° C. 100° C. 105° C. (105 − 95) Example 15 100:3  6,000 1918.5 21.2 23.4 4.9 Example 16 100:3 15,000 19 26.3 30.3 34.0 7.7

TABLE 5 Coating properties R (Å) σ (Å) Example 15 350 60.0 Example 16570 111.0 

Additionally, resist patterns obtained in Examples 15 and 16 had a goodpattern form with no scum.

It is seen from the above Tables 4 and 5 that novolak resin with asmaller molecular weight provides more preferable sensitivity differenceΔS (difference in sensitivity between the sensitivity attained by bakingat 105° C. and that at 95° C.) which is resulting from the difference incoating properties and baking conditions, that is, more preferableuniformity in line width of resist pattern which depends upon processingconditions. Additionally, smaller ΔS means that a formed pattern suffersless dimensional change even when there arises difference in temperaturedue to temperature distribution in the same substrate upon being exposedin a definite exposure amount, that is, the resist layer has anexcellent line width uniformity.

Example 17

100 parts by weight of a 100:3 mixture of novolak resin having a weightaverage molecular weight of 15,000 and polymethyl methacrylate (PMMA)having a weight average molecular weight of 10,000 and 20 parts byweight of an esterification product between2,3,4,4′-tetrahydroxy-benzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved inpropylene glycol monomethyl ether acetate and, for preventing formationof radial wrinkles, so-called striation, on a resist layer upon spincoating, 300 ppm of a fluorine-containing surfactant, Fluorad-472(manufactured by Sumitomo 3M Co.) was added thereto. After stirring themixture, it was filtered through a 0.2-μm filter to prepare a radiationsensitive composition of the present invention. Dissolution rate of thiscomposition was calculated according to the foregoing “method ofmeasuring dissolution rate of a radiation sensitive composition”. Inaddition, sensitivity of the radiation sensitive composition wasobserved according to the method of measuring sensitivity described inexample 13 to obtain results shown in Table 6.

Examples 18 to 21 and Comparative Examples 4 to 6

procedure conducted in the same manner as in Example 17 exect forchanging the mixing ratio of novolak resin to PMMA and the amount of theradiation sensitive material as shown in Table 6 to obtain the resultstabulated in Table 6.

TABLE 6 Amount of an added radiation sensitive material Novolak relativeto 100 resin: parts by weight PMMA of novolak Dis- Sensi- (ratio byresin solutionrate tivity weight) (parts by weight) (Å/min) (Mj/cm²)Example 17 100:3 20  120 35 Example 18 100:3 15 2100 25 Example 19 100:310 3710 24 Example 20 100:5 5  120 50 Example 21 100:5 1 1500 60Comparative 100:5 0.5 2400 180  Example 4 Comparative 100:0 1 33000  Nopattern Example 5 formed Comparative 100:0 15 22800  No pattern Example6 formed

Examples 22 to 26 and Comparative Example 7

Procedures were conducted in the same manner as in Example 17 except forchanging PMMA to poly(methyl methacrylate-co-styrene) [P(MMA-St)] havinga weight average molecular weight of about 10,000 and the mixing ratioof P(MMA-St) to novolak resin and the amount of the radiation sensitivematerial as shown in Table 7 to obtain the results tabulated in Table 7.

TABLE 7 Amount of an added radiation sensitive material Novolak relativeto 100 resin: parts by weight P(MMA-St) of novolak Dis- Sensi- (ratio byresin solutionrate tivity weight) (parts by weight) (Å/min) (mJ/cm²)Example 22 100:3 20  110 32 Example 23 100:3 15 1900 23 Example 24 100:310 3350 22 Example 25 100:5 5  110 45 Example 26 100:5 1 1350 53Comparative 100:5 0.5 2100 90 Example 7

It is seen from the above Tables 6 and 7 that practicable sensitivitycan be obtained with maintaining high layer-remaining properties byadjusting dissolution rate in a 2.38 weight-% tetramethylammoniumhydroxide solution of the radiation sensitive composition to 5000 Å/minor less and using the radiation sensitive material in an amount of 1part by weight or more per 100 parts by weight of the resin composition.Additionally, resist patterns obtained in Examples 17 to 26 had a goodpattern form with no scum.

Example 27

Procedures were conducted in the same manner as in Example 17 except forusing 100 parts by weight of a 100:3 mixture of novolak resin having aweight average molecular weight of 6,000 and an acrylic copolymercomposed of methyl methacrylate, n-butyl methacrylate and acrylic acidin a monomer ratio of 50:50:1 (weight ratio) and having a weight averagemolecular in weight of 13,000 and 19 parts by weight of theesterification product between 2,3,4,4′-tetrahydroxy-benzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride. The radiation sensitivecomposition showed a dissolution rate in an alkali solution of 570 Å/minand had a sensitivity of 25 mJ/cm². Additionally, the obtained resistpattern had a good pattern form with no scum.

Example 28

Procedures were conducted in the same manner as in Example 27 except forusing a copolymer composed of methyl methacrylate, n-butyl methacrylateand acrylic acid in a monomer ratio of 70:30:1 (weight ratio) and havinga weight average molecular weight of 13,000 as the acrylic copolymer.The radiation sensitive composition showed a dissolution rate in analkali solution of 590 Å/min and had a sensitivity of 20 mJ/cm². Theobtained resist pattern had a good pattern form with no scum.

Example 29

Procedures were conducted in the same manner as in Example 27 except forusing a copolymer composed of methyl methacrylate and n-butylmethacrylate in a monomer ratio of 70:30 (weight ratio) and having aweight average molecular weight of 13,000 as the acrylic copolymer. Theradiation sensitive composition showed a dissolution rate in an alkalisolution of 550 Å/min and had a sensitivity of 22 mJ/cm². The obtainedresist pattern had a good pattern form with no scum.

The results obtained in Examples 27 to 29 were shown in Table 8.

TABLE 8 Amount of an added radiation Novolak sensitive resin: materialper acrylic 100 parts by copolymer weight of Dissolution (ratio bynovolak resin rate Sensitivity weight) (parts by weight) (Å/min)(mJ/cm²) Example 27 100:3 19 570 25 Example 28 100:3 19 590 20 Example29 100:3 19 550 22

Example 30

100 parts by weight of a mixture of novolak resin having a weightaverage molecular weight of 6,000 and the polymer described in SynthesisExample 1 in a mixing ratio of 100:3 (by weight) and 19 parts by weightof an esterification product between 2,3,4,4′-tetrahydroxybenzophenoneand 1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved inpropylene glycol monomethyl ether acetate and, for preventing formationof radial wrinkles, so-called striation, on a resist layer upon spincoating, 300 ppm of a fluorine-containing surfactant, Fluorad-472(manufactured by Sumitomo 3M Co.) was added thereto. After stirring themixture, it was filtered through a 0.2-μm filter to prepare a radiationsensitive composition of the present invention. Sensitivity and resistlayer-remaining ratio of the composition were measured. Additionally,sensitivity was measured in the same manner as in Example 13. Resultsthus obtained are tabulated in Table 9.

Example 31

Procedures were conducted in the same manner as in Example 30 except forusing the polymer described in Synthesis Example 2 in place of thepolymer described in Synthesis Example 1 to obtain results tabulated inTable 9.

Example 32

Procedures were conducted in the same manner as in Example 30 except forusing the polymer described in Synthesis Example 5 in place of thepolymer described in Synthesis Example 1 to obtain results tabulated inTable 9.

Example 33

Procedures were conducted in the same manner as in Example 30 except forusing 100 parts by weight of a mixture of novolak resin having a weightaverage molecular weight of 6,000 and the polymer described in SynthesisExample 2 in a mixing ratio of 100:3 (by weight) and 4 parts by weightof an esterification product between 2,3,4,4′-tetrahydroxybenzophenoneand 1,2-naphthoquinonediazide-5-sulfonyl chloride to obtain resultstabulated in Table 9.

Example 34

Procedures were conducted in the same manner as in Example 30 except forusing the polymer described in Synthesis Example 3 in place of thepolymer described in Synthesis Example 1 to obtain results tabulated inTable 9.

Example 35

Procedures were conducted in the same manner as in Example 30 except forusing the polymer described in Synthesis Example 4 in place of thepolymer described in Synthesis Example 1 to obtain results tabulated inTable 9.

Example 36

Procedures were conducted in the same manner as in Example 30 except forusing the polymer described in Synthesis Example 6 in place of thepolymer described in Synthesis Example 1 to obtain results tabulated inTable 9.

Comparative Example 8

Procedures were conducted in the same manner as in Example 30 except fornot using the polymer described in Synthesis Example 1 to obtain resultstabulated in Table 9.

Comparative Example 9

Procedures were conducted in the same manner as in Example 33 except forchanging the amount of an added esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride relative to 100 parts byweight of novolak resin having a weight average molecular weight of6,000 to 4 parts by weight and not using the polymer described inSynthesis Example 2 to obtain results tabulated in Table 9.

Comparative Example 10

Procedures were conducted in the same manner as in Example 30 except forusing 25 parts by weight of an esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride relative to 100 parts byweight of novolak resin having a weight average molecular weight of10,000 and not using the polymer described in Synthesis Example 1 toobtain results tabulated in Table 9.

TABLE 9 Amount of added Resist Acrylic resin radiation layer- AcidAmount sensitive remaining Copolymerizable value added materialSensitivity ratio components* Mw (mgKOH/g) (phr**) (phr**) (mJ/cm²) (%)Example 30 MMA, tBuMA, AA 15,000 80 300/103 19 16.8 96.0 Example 31 MMA,tBuMA, AA 13,000 8 As above 19 17.6 97.0 Example 32 MMA, tBuMA, AA13,000 1 As above 19 18.4 98.2 Example 33 MMA, tBuMA, AA 13,000 8 Asabove 4 25.3 97.0 Example 34 MMA, nBuMA, AA 13,000 8 As above 19 16.497.5 Example 35 MMA, cHMA, AA 12,000 8 As above 19 17.8 97.3 Example 36MMA, tBUMA 13,000 0.3 As above 19 22.0 98.8 Comparative — — — 0 19 Nopattern No pattern Example 8 formed formed Comparative — — — 0 4 Nopattern No pattern Example 9 formed formed Comparative — — — 0 25 35.097.0 Example 10 *MMA: methyl methacrylate, tBuMA: t-butyl metacrylate.AA: acrylic acid, cHMA: cyclohexyl methacrylate, nBuMA: n-butylmethacrylate **amount relative to 100 parts by weight of resin in aradiation sensitive composition (parts by weight)

Additionally, resist patterns obtained in Examples 30 to 36 had goodline width uniformity and good form with no scum.

However, it is seen from the above Table 9 that, if acid value of theacrylic resin is out of the range of 1 to 80 mg KOH/g, sensitivity issomewhat decreased when the amount of the radiation sensitive materialadded is 19 parts by weight and that, if acid value of the acrylic resinis in the range of 1 to 80 mg KOH/g, there is obtained a radiationsensitive composition which are good in both sensitivity and resistlayer-remaining ratio even when the amount of the radiation sensitivematerial added is decreased, thus acid value of the acrylic resin beingpreferably 1 to 80 mg KOH/g. Additionally, if acrylic resins are notused, resist layer-remaining ratio of the radiation sensitivecomposition is too bad to form patterns.

Example 37

(NMR Measurement of Resin Composition)

¹H-NMR spectrum in a heavy acetone solution of a resin compositionprepared by mixing novolak resin having a weight average molecularweight of 10,000 and poly-n-butyl methacrylate having a weight averagemolecular weight of 13,000 in a mixing ratio of 100:3 (by weight) wasmeasured. Integrated value A of area beneath the peaks in a range of 7.2to 5.6 ppm in the obtained NMR chart and integrated value B of areabeneath the peaks in the range of 1.3 to 0.95 ppm excluding area beneaththe peak of the solvent of propylene glycol monomethyl ether acetatewere calculated, and a value of B/A, that is X, was determined to be0.042.

Additionally, when NMR spectrum was measured with respect to a sampleprepared from a resist film obtained by using a radiation sensitivecomposition prepared below in place of the above-described resin film,there was obtained the same X value as that obtained with respect to theresin composition.

(Preparation of a Radiation Sensitive Composition)

100 parts by weight of the resin composition described above and 18parts by weight of an esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved inpropylene glycol monomethyl ether acetate and, for preventing formationof radial wrinkles, so-called striation, on a resist layer upon spincoating, 300 ppm of a fluorine-containing surfactant, Fluorad-472(manufactured by Sumitomo 3M Co.) was added thereto. After stirring themixture, it was filtered through a 0.2-μm filter to prepare a radiationsensitive composition of the present invention.

Sensitivity and resist layer-remaining ratio of the composition weremeasured. Additionally, sensitivity and coating properties were measuredin the same manner as in Example 13. Results thus obtained are tabulatedin Table 10.

Example 38

Procedures were conducted in the same manner as in Example 37 except forusing poly(methyl methacrylate-co-n-butyl methacrylate) [70:30] having aweight average molecular weight of 13,000 in place of the poly-n-butylmethacrylate to obtain results tabulated in Table 10.

Example 39

Procedures were conducted in the same manner as in Example 37 except forusing poly(methyl methacrylate-co-n-butyl methacrylate-co-acrylic acid)[70:29:1] having a weight average molecular weight of 13,000 in place ofthe poly-n-butyl methacrylate to obtain results tabulated in Table 10.

Example 40

Procedures were conducted in the same manner as in Example 37 except forusing a mixture of polymethyl methacrylate having a weight averagemolecular weight of 13,000 and poly-n-butyl methacrylate in amixing-ratio of 70:30 in place of the poly-n-butyl methacrylate toobtain results tabulated in Table 10.

Comparative Example 11

¹H-NMR spectrum in a heavy acetone solution of novolak resin having aweight average molecular weight of 10,000 was measured. A value of X, orB/A wherein A represents an integrated area beneath the peaks in a rangeof 7.2 to 5.6 ppm in the obtained NMR chart and B represents anintegrated area beneath the peaks in the range of 1.3 to 0.95 ppm wasdetermined to be 0.

100 parts by weight of the above-described resin and 23 parts by weightof the esterification product between 2,3,4,4′-tetrahydroxybenzophenoneand 1,2-naphthoquinonediazide-5-sulfonyl chloride were dissolved inpropylene glycol monomethyl ether acetate, and subsequent procedureswere conducted in the same manner as in Example 37, followed byevaluation of sensitivity, resist layer-remaining ratio and coatingproperties. Results thus obtained are tabulated in Table 10.

Comparative Example 12

Procedures were conducted in the same manner as in Comparative Example11 except for changing the amount of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride to 18 parts by weight.Results thus obtained are tabulated in Table 10.

TABLE 10 Resist layer- Coating X = Sensitivity remaining ratioproperties B/A (mJ/cm²) (%) r (Å) σ (Å) Example 37 0.042 27 96 360  50Example 38 0.042 25 96 350  47 Example 39 0.042 23 96 350  47 Example 400.042 25 96 350  52 Comparative 0 40 85 620 100 Example 11 Comparative 0No pattern  0 — — Example 12 formed

Example 41

Procedures were conducted in the same manner as in Example 37 except forchanging the mixing ratio of novolak resin and poly-n-butyl methacrylateused in Example 37 to 100:10 by weight and the amount of theesterification product between 2,3,4,4′-tetrahydroxybenzophenone and1,2-naphtho-quinonediazide-5-sulfonyl chloride to 12 parts by weight.Then sensitivity and resist layer-remaining ratio of the compositionwere evaluated. Results thus obtained are tabulated in Table 11.

Example 42

Procedures were conducted in the same manner as in Example 41 except forusing poly(methyl methacrylate-co-n-butyl methacrylate) [70:30] having aweight average molecular weight of 13,000 in place of poly-n-butylmethacrylate to obtain results tabulated in Table 11.

Example 43

Procedures were conducted in the same manner as in Example 41 except forusing poly(methyl methacrylate-co-n-butyl methacrylate-co-acrylic acid)[70:29:1] having a weight average molecular weight of 13,000 in place ofpoly-n-butyl methacrylate to obtain results tabulated in Table 11.

Example 44

Procedures were conducted in the same manner as in Example 41 except forusing a mixture of polymethyl methacrylate having a weight averagemolecular weight of 13,000 and poly-n-butyl methacrylate in mixing ratioof 70:30 in place of poly-n-butyl methacrylate to obtain resultstabulated in Table 11.

Comparative Example 13

Procedures were conducted in the same manner as in Example 41 except fornot using poly-n-butyl methacrylate to obtain results tabulated in Table11.

TABLE 11 Resist layer-remaining Sensitivity ratio X = B/A (mJ/cm²) (%)Example 41 0.12 80 100 Example 42 0.12 70 100 Example 43 0.12 60 100Example 44 0.12 70 100 Comparative 0 No pattern  0 Example 13 formed

Example 45

Procedures were conducted in the same manner as in Example 37 except forchanging a mixing ratio of novolak resin and poly-n-butyl methacrylateto 100:0.25 by weight and the amount of the esterification productbetween 2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride to 23 parts by weight toobtain results tabulated in Table 12.

Example 46

Procedures were conducted in the same manner as in Example 45 except forusing poly(methyl methacrylate-co-n-butyl methacrylate) [70:30] having aweight average molecular weight of 13,000 in place of poly-n-butylmethacrylate to obtain results tabulated in Table 12.

Example 47

Procedures were conducted in the same manner as in Example 45 except forusing poly(methyl methacrylate-co-n-butyl methacrylate-co-acrylic acid)[70:29:1] having a weight average molecular weight of 13,000 in place ofpoly-n-butyl methacrylate to obtain results tabulated in Table 12.

TABLE 12 Resist layer-remaining Sensitivity ratio X = B/A (mJ/cm²) (%)Example 45 0.012 40 92 Example 46 0.012 40 92 Example 47 0.012 40 92

It is seen from Table 12 that even when the mixed resin is added in asmall amount, sensitivity and resist layer-remaining ratio can beimproved.

Additionally, a chart obtained by measuring ¹H-NMR spectrum of a samplefilm formed by a mixed resin consisting of novolak resin and acrylicpolymer (100:10) is shown in FIG. 1, and a chart obtained by measuring¹H-NMR spectrum of a resist film sample formed by using a radiationsensitive composition containing this mixed resin is shown in FIG. 2. Asis shown in these charts obtained with the mixed resin film sample andthe resist film sample, respectively, they are scarcely different fromeach other in the value of X, or B/A wherein A represents an integratedarea beneath the peaks in a range of 7.2 to 5.6 ppm in the obtained NMRchart and B represents an integrated area beneath the peaks in the rangeof 1.3 to 0.95 ppm excluding integrated area beneath the peak of thesolvent of propylene glycol monomethyl ether acetate, though somedifference in spectrum is observed based on the difference in componentscontained in the samples. This is not limited to the resin compositionused for obtaining the charts but applies to the resin composition ofeach of the above-described Examples. Example 37 specificallydemonstrates this, but with respect to each of the resin compositionused in other Examples, too, the X value obtained with resin film sampleand the X value with resist film sample were substantially the same.

Example 48

To 100 parts by weight of novolak resin having a weight averagemolecular weight of 7,000, 20 parts by weight of an esterificationproduct between 2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride and 3.0 parts by weight ofpolystyrene (PSt) having a weight average molecular weight of 14,000were dissolved in propylene glycol monomethyl ether acetate and, forpreventing formation of radial wrinkles, so-called striation, on aresist layer upon spin coating, 300 ppm of a fluorine-containingsurfactant, Fluorad-472 (manufactured by Sumitomo 3M Co.) was addedthereto. After stirring the mixture, it was filtered through a 0.2-μmfilter to prepare a radiation sensitive composition of the presentinvention. This composition was spin-coated on a 4-inch silicon wafer,and baked on a hot plate at 100° C. for 90 seconds to obtain a 1.5-μmthick resist layer. This resist layer was exposed with various exposureenergies by a g-line stepper made by Nikon Co. (FX-604F) through a testpattern with line and space patterns having various line and spacewidths and a line-to-space width ratio of 1:1, and developed in a 2.38weight-% aqueous solution of tetramethylammonium hydroxide at 23° C. for60 seconds. Resist layer-remaining ratio was determined based on thethickness of resist before and after development. In addition, an energyamount enough to resolve a 5-μm line-and-space pattern to 1:1 isdetermined by observation, which was taken as a sensitivity. Thus, therewas obtained the result shown in Table 13.

Example 49

Procedures were conducted in the same manner as in Example 48 except forusing polystyrene (PSt) having a weight average molecular weight of7,000 in place of polystyrene (PSt) having a weight average molecularweight of 14,000 to obtain results tabulated in Table 13.

Example 50

Procedures were conducted in the same manner as in Example 48 except forusing poly(styrene-co-methyl methacrylate) [90:10] (PSt/MMA) having aweight average molecular weight of 7,000 in place of polystyrene (PSt)having a weight average molecular weight of 14,000 to obtain resultstabulated in Table 13.

Example 51

Procedures were conducted in the same manner as in Example 48 except forusing 5 parts by weight of o-cresol of a low molecular compound havingphenolic hydroxyl group or groups, 21.5 parts by weight of anesterification product between 2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride and 3.2 parts by weight ofpolystyrene (PSt) having a weight average molecular weight of 14,000relative to 100 parts by weight of novolak resin having a weight averagemolecular weight 7,000, to obtain results tabulated in Table 13.

Comparative Example 14

Procedures were conducted in the same manner as in Example 48 except fornot using polystyrene (PSt) having a weight average molecular weight of14,000 to obtain results tabulated in Table 13.

Example 52

Procedures were conducted in the same manner as in Example 48 except forusing polymethyl methacrylate (PMMA) having a weight average molecularweight of 10,000 in place of polystyrene (PSt) having a weight averagemolecular weight of 14,000 to obtain results tabulated in Table 13.

TABLE 13 Resist layer- Resin coupled with remaining ratio Sensitivitynovolak resin (%) (mJ/cm²) Example 48 PSt 98.5 23.9 Example 49 PSt 99.028.9 Example 50 PSt/MMA 99.3 32.0 Example 51 PSt 98.2 21.0 (with a lowmolecular compound having a phenolic hydroxyl group) Comparative — 52.0— Example 14 (No pattern formed) Example 52 PMMA 98.0 35.0

Example 53

Procedures were conducted in the same manner as in Example 48 except forchanging the amount of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride to 25 parts by weight toobtain results tabulated in Table 14.

Comparative Example 15

Procedures were conducted in the same manner as in Example 53 except fornot using polystyrene (PSt) having a weight average molecular weight of14,000 to obtain results tabulated in Table 14.

TABLE 14 Resin coupled Resist layer- with novolak remaining ratioSensitivity resin (%) (mJ/cm²) Example 53 PSt 100.0 32.0 Comparative — 92.0 32.0 Example 15

Example 54

Procedures were conducted in the same manner as in Example 48 except forusing 30 parts by weight of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride relative to 100 parts byweight of novolak resin having a weight average molecular weight of5,000 to obtain results tabulated in Table 15.

Comparative Example 16

Procedures were conducted in the same manner as in Example 54 except fornot using polystyrene (PSt) having a weight average molecular weight of14,000 to obtain results tabulated in Table 15.

TABLE 15 Resin coupled Resist layer- with novolak remaining ratioSensitivity resin (%) (mJ/cm²) Example 54 PSt 100.0 26.0 Comparative — 92.0 25.0 Example 16

Example 55

Procedures were conducted in the same manner as in Example 48 except forusing 10 parts by weight of the esterification product between2,3,4,4′-tetrahydroxybenzophenone and1,2-naphthoquinonediazide-5-sulfonyl chloride and 4.0 parts by weight ofpolystyrene (PSt) having a weight average molecular weight of 14,000relative to 100 parts by weight of novolak resin having a weight averagemolecular weight of 10,000 to obtain results tabulated in Table 16.

Comparative Example 17

Procedures were conducted in the same manner as in Example 55 except fornot using polystyrene (PSt) having a weight average molecular weight of14,000 to obtain results tabulated in Table 16.

TABLE 16 Resin coupled Resist layer- with novolak remaining ratioSensitivity resin (%) (mJ/cm²) Example 55 PSt 98.5 27.0 Comparative — Nopattern — Example 17 formed

Resist patterns obtained according to Examples 48 to 55 had no scum. Inaddition, the resist patterns had a good pattern form and gooduniformity of line width. It is seen from Tables 13 to 16 that even whenstyrenic resin is used as the resin additive, radiation sensitivecompositions are obtained with high sensitivity and good resistlayer-remainlng ratio. Additionally, it is seen from table 13 that whenPMMA is selected as a resin coupled with novolak resin, sensitivity andresist layer-remaining ratio are improved, and when PSt is used, aradiation sensitive composition having higher sensitivity than that whenPMMA being used is obtained. It may be considered that the improvementof sensitivity is attained by following reason. That is, refractiveindexes of PMMA and PSt used in the present invention are different fromthat of novolak resin, therefore sensitivity of the radiation sensitivecomposition is improved. On the other hand, difference in refractiveindex of novolak resin and PSt is smaller than that of novolak resin andPMMA. The difference in refractive index of novolak resin and PSt ismore suitable than that of novolak resin and PMMA in viewpoint ofimprovement of sensitivity to improve utilization efficiency ofradiation sensitive materials. Further, it is seen from Table 15 thatwhen styrenic resin is used as a resin additive, high sensitivity andgood resist layer-remaining ratio of the radiation sensitive compositioncan be maintained even if much radiation sensitive material are addedthereto in the present invention, that is, low process dependency can beattained.

Advantages of the Invention

According to the first present invention, working effects of a radiationsensitive material can be enhanced by using, as resins for the resincomposition to be used in the radiation sensitive composition, at leastone set of resins different from each other in refractive index (Δn) by0.03 or more. Thus, it becomes possible to reduce the amount of theradiation sensitive material in the radiation sensitive composition andimprove throughput by enhancing sensitivity of the radiation sensitivecomposition. According to the second present invention, a radiationsensitive composition can be obtained which shows excellent resistlayer-remaining ratio even when the amount of radiation sensitivematerial is reduced with attempting to enhance sensitivity of theradiation sensitive material, by incorporating as the resin additive aresin capable of working as a dissolution inhibitor into a radiationsensitive composition comprising an alkali-soluble resin and a radiationsensitive material containing quinonediazide group or groups. Inaddition, according to the present invention, there can be manufactureda radiation sensitive composition which has a high resolution, gooddevelopability, and excellent pattern-forming properties and, further, aradiation sensitive composition having excellent coating properties,forming a resist pattern with an excellent line width uniformity andshowing low process dependency.

As is described above, the present invention enables one to obtain aradiation sensitive composition having a high sensitivity and excellentproperties such as excellent developability, resist layer-remainingproperties, coating properties and line width uniformity of a resistpattern, with decreasing the amount of radiation sensitive materialused. Thus, the present invention enables one to remarkably reduce thecost of manufacturing semiconductor integrated circuits, FPD, circuitbases for thermal head, etc. by improving throughput due to enhancementof sensitivity and by decreasing the amount of radiation sensitivematerial.

Industrial Utility

As has been described in detail hereinbefore, the radiation sensitivecomposition of the present invention is favorably used as a photoresistmaterial for use in manufacturing semiconductor integrated circuits suchas LSI, manufacturing FPD, and manufacturing circuit bases for thermalhead.

What is claimed is:
 1. A radiation sensitive composition comprising aresin composition and a radiation sensitive material, wherein the resincomposition comprises at least (a) an alkali-soluble novolak resin and(b) a resin additive selected from the group consisting of polyacrylicester, polymethacrylic ester, polystyrene derivatives, polyvinylbenzoate, polyvinyl phenyl acetate, polyvinyl acetate, polyvinylchloroacetate, polyacrylonitrile, poly-α-methylacrylonitrile, polyvinylphthalimide, and copolymers obtained from two or more monomers selectedfrom acrylic ester, methacrylic ester, styrene derivatives, vinylbenzoate, vinyl phenyl acetate, vinyl acetate, vinyl chloroacetate,acrylonitrile, α-methylacrylonitrile, N-vinyl phthalimide, N-vinylimidazole, N-vinyl carbazole, 2-vinyl quinoline, vinyl cyclohexane,vinyl naphthalene, vinyl pyridine and N-vinyl pyrrolidone, whereinpolyacrylic ester of a resin additive is one member selected from thegroup of polymethyl acrylate, polyethyl acrylate, poly-n-propylacrylate, poly-n-butyl acrylate, poly-n-hexyl acrylate, polylsopropylacrylate, polyisobutyl acrylate, poly-t-butyl acrylate, polycyclohexylacrylate, polybenzyl acrylate, poly-2-chloroethyl acrylate,polymethyl-α-chloroacrylate, polyphenyl α-bromoacrylate or a copolymertherefrom and polymethacrylic ester of a resin additive is one memberselected from the group of polymethyl methacrylate, polyethylmethacrylate, poly-n-propyl methacrylate, poly-n-butyl methacrylate,poly-n-hexyl methacrylate, polyisopropyl methacrylate, polyisobutylmethacrylate, poly-t-butyl methacrylate, polycyclohexyl methacrylate,polybenzyl methacrylate, polyphenyl methacrylate, poly-1-phenylethylmethacrylate, poly-2-phenylethyl methacrylate, polyfurfurylmethacrylate, polydiphenylmethyl methacrylate, polypentachlorophenylmethacrylate, polynaphthyl methacrylate or a copolymer therefrom and theradiation sensitive material is (c) a radiation sensitive materialcontaining a quinonediazide group.
 2. A radiation sensitive compositioncomprising a resin composition and a radiation sensitive material,wherein the resin composition comprises two or more kinds of resins of(a) an alkali-soluble novolak resin and (b) a resin additive selectedfrom the group consisting of polyacrylic ester, polymethacrylic ester,polystyrene derivatives, polyvinyl benzoate, polyvinyl phenyl acetate,polyvinyl acetate, polyvinyl chloroacetate, polyacrylonitrile,poly-α-methylacrylonitrile, polyvinyl phthalimide, and copolymersobtained from two or more monomers selected from acrylic ester,methacrylic ester, styrene derivatives, vinyl benzoate, vinyl phenylacetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidazole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone, wherein polyacrytic ester of aresin additive is one member selected from the group of polymethylacrylate, polytethyl acrylate, poly-n-propyl acrylate, poly-n-butylacrylate, poly-n-hexyl acrylate, polyisopropyl acrylate, polyisobutylacrylate, poly-t-butyl acrylate, polycyclohexyl acrylate, polybenzylacrylate, poly-2-chloroethyl acrylate, polymethyl-α-chloroacrylate,polyphenyl α-bromoacrylate or a copolymer therefrom, and polymethacrylicester of a resin additive is one member selected from the group ofpolymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polyenzyl methacrylate,polyphenyl methacrylate, poly-1-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate or a copolymer therefrom, wherein the resinadditive is a copolymer obtained from at least two monomers selectedfrom acrylic esters, methacrylic esters and styrene derivatives, and acopolymer obtained from at least one of these monomers and an organicacid monomer having a carboxyl group or a carboxylic anhydride group. 3.The radiation sensitive composition according to claim 2, wherein acopolymer obtained from at least one monomer selected from acrylicesters, methacrylic esters and styrene derivatives and an organic acidmonomer having a carboxyl group or a carboxylic anhydride group has anacid value of 1 to 80 mg KOH/g.
 4. The radiation sensitive compositionaccording to claim 2, further comprising a polymer-containing 50 mole-%or more of a repeating unit having a carboxyl group or a carboxylicanhydride group.
 5. A radiation sensitive composition comprising a resincomposition and a radiation sensitive material, wherein the resincomposition comprises two or more kinds of resins of (a) analkali-soluble novolak resin and (b) a resin additive selected from thegroup consisting of polyacrylic ester, polymethacrylic ester,polystyrene derivatives, polyvinyl benzoate, polyvinyl phenyl acetate,polyvinyl acetate, polyvinyl chloroacetate, polyacrylonitrile,poly-α-methylacrylonitrile, polyvinyl phthalimide, and copolymersobtained from two or more monomers selected from acrylic ester,methacrylic ester, styrene derivatives, vinyl benzoate, vinyl phenylacetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidazole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone, wherein polyacrylic ester of aresin additive is one member selected from the group of polymethylacrylate, polyethyl acrylate, poly-n-propyl acrylate, poly-n-butylacrylate, poly-n-hexyl acrylate, polyisopropyl acrylate, polyisobutylacrylate, poly-t-butyl acrylate, polycyclohexyl acrylate, polybenzylacrylate, poly-2-chloroethyl acrylate, polymethyl-α-chloroacrylate,polyphenyl α-bromoacrylate or a copolymer therefrom, and polymethacrylicester of a resin additive is one member selected from the group ofpolymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate,polyphenyl methacrylate, poly-1-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate or a copolymer therefrom, wherein thedissolution rate in 2.38 weight-% aqueous tetramethylammonium hydroxideof the radiation sensitive composition is not more than 5000 Å/min.
 6. Aradiation sensitive composition comprising a resin composition and aradiation sensitive material, wherein the resin composition comprisestwo or more kinds of resins of (a) an alkali-soluble novolak resin and(b) a resin additive selected from the group consisting of polyacrylicester, polymethacrylic ester, polystyrene derivatives, polyvinylbenzoate, polyvinyl phenyl acetate, polyvinyl acetate, polyvinylchloroacetate, polycrylonitrile, poly-α-methylacrylonitrile, polyvinylphthalimide, and copolymers obtained from two or more monomers selectedfrom acrylic ester, methacrylic ester, styrene derivatives, vinylbenzoate, vinyl phenyl acetate, vinyl acetate, vinyl chloroacetate,acrylonitrile, α-methylacrylonitrile, N-vinyl phthalimide, N-vinylimidazole, N-vinyl carbazole, 2-vinyl quinoline, vinyl cyclohexane,vinyl naphthalene, vinyl pyridine and N-vinyl pyrrolidone, whereinpolyacrylic ester of a resin additive is one member selected from thegroup of polymethyl acrylate, polyethyl acrylate, poly-n-propylacrylate, poly-n-butyl acrylate, poly-n-hexyl acrylate, polyisopropylacrylate, polyisobutyl acrylate, poly-t-butyl acrylate, polycyclohexylacrylate, polybenzyl acrylate, poly-2-chloroethyl acrylate,polymethyl-α-chloroacrylate, polyphenyl α-bromoacrylate or a copolymertherefrom, and polymethacrylic ester of a resin additive is one memberselected from the group of polymethyl methacrylate, polyethylmethacrylate, poly-n-propyl methacrylate, poly-n-butyl methacrylate,poly-n-hexyl methacrylate, polyisopropyl methacrylate, polyisobutylmethacrylate, poly-t-butyl methacrylate, polycyclohexyl methacrylate,polybenzyl methacrylate, polyphenyl methacrylate, poly-1-phenylethylmethacrylate, poly-2-phenylethyl methacrylate, polyfurfurylmethacrylate, polydiphenylmethyl methacrylate, polypentachlorophenylmethacrylate, polynaphthyl methacrylate or a copolymer therefrom whereinwhen the resin containing styrenic monomer-repeating units of less than50 mole-% of repeating units in the resin is used as the resin additive,the weight average molecular weight of the resin is 7,000 to 20,000 asdetermnined by polystyrene standards and when the resin containingstyrene derivative-repeating units of not less than 50 mole-% ofrepeating units in the resin is used as the resin additive, the weightaverage molecular weight of the resin is 3,000 to 25,000 as determinedby polystyrene standards.
 7. The radiation sensitive compositionaccording to claim 2, wherein the value of X which is B/A is in therange of 0.01 to 0.13 whereupon A is an integrated area beneath peaks inthe range of 7.2 to 5.6 ppm and B is an integrated area beneath peaks inthe range of 1.3 to 0.95 ppm in a H-NMR spectrum of a solution of theresin composition in heavy acetone.
 8. A radiation sensitive compositioncomprising a resin composition and a radiation sensitive material,wherein the resin composition comprises two or more kinds of resins of(a) an alkali-soluble novolak resin and (b) a resin additive selectedfrom the group consisting of polyacrylic ester, polymethacrylic ester,polystyrene derivatives, polyvinyl benzoate, polyvinyl phenyl acetate,polyvinyl acetate, polyvinyl chloroacetate, polyacrylonitrile,poly-α-methylacrylonitrile, polyvinyl phthalimide, and copolymersobtained from two or more monomers relected from acrylic ester,methacrylic ester, styrene derivatives, vinyl benzoate, vinyl phenylacetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidazole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone, wherein polyacrylic ester of aresin additive is one member selected from the group of polymethylacrylate, polyethyl acrylate, poly-n-propyl acrylate, poly-n-butylacrylate, poly-n-hexyl acrylate, polyisopropyl acrylate, polyisobutylacrylate, poly-t-butyl acrylate, polycyclohexyl acrylate, polybenzylacrylate poly-2-chloroethyl acrylate, polymethyl-α-chloroacrylate,polyphenyl α-bromoacrylate or a copolymer therefrom, and polymethacrylicester of a resin additive is one member selected from the group ofpolymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate,polyphenyl methacrylate, poly-1-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate or a copolymer therefrom, wherein the weightaverage molecular weight of the novolak resin is 3,000 to 15,000 asdetermnined by polystyrene standards.
 9. A radiation sensitivecomposition comprising a resin composition and a radiation sensitivematerial, wherein the resin composition comprises two or more kinds ofresins of (a) an alkali-soluble novolak resin and (b) a resin additiveselected from the group consisting of polyacrylic ester, polymethacrylicester, polystyrene derivatives, polyvinyl benzoate, polyvinyl phenylacetate, polyvinyl acetate, polyvinyl chloroacetate, polyacrylonitrile,poly-α-methylacrylonitrile, polyvinyl phthalimide, and copolymersobtained from two or more monomers selected from acrylic ester,methacrylic ester, styrene derivatives, vinyl benzoate, vinyl phenylacetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidazole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone, wherein polyacrylic ester of aresin additive is one member selected from the group of polymethylacrylate, polyethyl acrylate, poly-n-propyl acrylate, poly-n-butylacrylate, poly-n-hexyl acrylate, polyisopropyl acrylate, polyisobutylacrylate, poly-t-butyl acrylate, polycyclohexyl acrylate, polybenzylacrylate, poly-2-chloroethyl acrylate, polymethyl-α-chloroacrylate,polyphenyl α-bromoacrylate or a copolymer therefrom, and polymethacrylicester of a resin additive is one member selected from the group ofpolymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate,polyphenyl methacrylate, poly-1-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate or a copolymer therefrom wherein when a resincontaining styrenic monomer-repeating units of less than 50 mole-% ofrepeating units in the resin is used as the resin additive, the amountof the radiation sensitive material is 1 to 20 parts by weight relativeto 100 parts by weight of the alkali-soluble resin in the radiationsensitive composition and when a resin containing styrenicmonomer-repeating units of not less than 50 mole-% of repeating units inthe resin is used as the resin additive, the amount of the radiationsensitive material is 10 to 30 parts by weight relative to 100 parts byweight of the alkali-soluble resin in the radiation sensitivecomposition.
 10. The radiation sensitive composition according to claim9, wherein when the resin containing styrenic monomer-repeating units ofless than 50 mole-% of repeating units in the resin is used as the resinadditive, the amount of the radiation sensitive material is 1 to 18parts by weight relative to 100 parts by weight of the alkali-solubleresin in the radiation sensitive composition.
 11. A radiation sensitivecomposition comprising a resin composition and a radiation sensitivematerial, wherein the resin composition comprises two or more kinds ofresins of (a) an alkali-soluble novolak resin and (b) a resin additiveselected from the group consisting of polyacrylic ester, polymethacrylicester, polystyrene derivatives, polyvinyl benzoate, polyvinyl phenylacetate, polyvinyl acetate, polyvinyl chloroacetate, polyacrylontrile,poly-α-methylacrylonitrile, polyvinyl phthalimide, and copolymersobtained from two or more monomers selected from acrylic ester,methacrylic ester, styrene derivatives, vinyl benzoate, vinyl phenylacetate, vinyl acetate, vinyl chloroacetate, acrylonitrile,α-methylacrylonitrile, N-vinyl phthalimide, N-vinyl imidozole, N-vinylcarbazole, 2-vinyl quinoline, vinyl cyclohexane, vinyl naphthalene,vinyl pyridine and N-vinyl pyrrolidone, wherein polyacrylic ester of aresin additive is one member selected from the group of polymethylacrylate, polyethyl acrylate, poly-n-propyl acrylate, poly-n-butylacrylate, poly-n-hexyl acrylate, polyisopropyl acrylate, polyisobutylacrylate, poly-t-butyl acrylate, polycyclohexyl acrylate, polybenzylacrylate poly-2-chloroethyl acrylate, polymethyl-α-chloroacrylate,polyphenyl α-bromoacrylate or a copolymer therefrom, and polymethacrylicester of a resin additive is one member selected from the group ofpolymethyl methacrylate, polyethyl methacrylate, poly-n-propylmethacrylate, poly-n-butyl methacrylate, poly-n-hexyl methacrylate,polyisopropyl methacrylate, polyisobutyl methacrylate, poly-t-butylmethacrylate, polycyclohexyl methacrylate, polybenzyl methacrylate,polyphenyl methacrylate, poly-1-phenylethyl methacrylate,poly-2-phenylethyl methacrylate, polyfurfuryl methacrylate,polydiphenylmethyl methacrylate, polypentachlorophenyl methacrylate,polynaphthyl methacrylate or a copolymer therefrom wherein when a resincontaining styrenic monomer-repeating units of less than 50 mole-% ofrepeating units in the resin is used as the resin additive, the contentof the resin additive 1 to 20 parts by weight relative to 100 parts byweight of novolak resin of the alkali-soluble resin and when a resincontaining styrenic monomer-repeating units of not less than 50 mole-%of repeating units in the resin is used as the resin additive, thecontent of the resin additive is 0.5 to 5 parts by weight relative to100 parts by weight of novolak resin of the alkali-soluble resin.
 12. Aradiation sensitive composition comprising a resin composition and aradiation sensitive material, wherein the resin composition comprisestwo or more kinds of resins of (a) an alkali-soluble novolak resin and(b) a resin additive selected from the group consisting of polyacrylicester, polymethacrylic ester, polystyrene derivatives, polyvinylbenzoate, polyvinyl phenyl acetate, polyvinyl acetate, polyvinylchloroacetate, polyacrylonitrile, poly-α-methylacrylonitrile, polyvinylphthalimide, and copolymers obtained from two or more monomers selectedfrom acrylic ester, methacrylic ester, styrene derivatives, vinylbenzoate, vinyl phenyl acetate, vinyl acetate, vinyl chloroacetate,acrylonitrile, α-methylacrylonitrile, N-vinyl phthalimide, N-vinylimidazole, N-vinyl carbazole, 2-vinyl quinoline, vinyl cyclohexane,vinyl naphthalene, vinyl pyridine and N-vinyl pyrrolidone, whereinpolyacrylic ester of a resin additive is one member selected from thegroup of polymethyl acrylate, polyethyl acrylate, poly-n-propylacrylate, poly-n-butyl acrylate, poly-n-hexyl acrylate, polyisopropylacrylate, polyisobutyl acrylate, poly-t-butyl acrylate, polycyclohexylacrylate, polybenzyl acrylate, poly-2-chloroethyl acrylate,polymethyl-α-chloroacrylate, polyphenyl α-bromoacrylate or a copolymertherefrom, and polymethacrylic ester of a resin additive is one memberselected from the group of polymethyl methacrylate, polyethylmethacrylate, poly-n-propyl methacrylate, poly-n-buty, methacrylate,poly-n-hexyl methacrylate, polyisopropyl methacrylate, polyisobutylmethacrylate, poly-t-butyl methacrylate, polycyclohexyl methacrylate,polybenzyl methacrylate, polyphenyl methacrylate, poly-1-phenylethylmethacrylate, poly-2-phenylethyl methacrylate, polyfurfurylmethacrylate, polydiphenylmethyl methacrylate, polypentachlorophenylmethacrylate, polynaphthyl methacrylate or a copolymer therefrom furthercomprising a low molecular compound having phenolic hydroxyl group orgroups represented by the general formula (I):

wherein R₁, R₂, R₃, R₄, R₅, R₆ and R₇ each represents independently H, aC₁ to C₄ alkyl group, a C₁ to C₄ alkoxyl group, a cyclohexyl group or agroup represented by the formula:

wherein R₈ represents H, a C₁ to C₄ alkyl group, a C₁ to C₄ alkoxylgroup or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b,c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5,c+d≦5, e+f≦5, and g+h≦5; and i is 0, 1 or
 2. 13. The radiation sensitivecomposition according to claim 1, wherein the resin additive is acopolymer obtained from at least two monomers selected from acrylicesters, methacrylic esters and styrene derivatives, and a copolymerobtained from at least one of these monomers and an organic acid monomerhaving a carboxyl group or a carboxylic anhydride group.
 14. Theradiation sensitive composition according to claim 13, wherein acopolymer obtained from at least one monomer selected from acrylicesters, methacrylic esters and styrene derivatives and an organic acidmonomer having a carboxyl group or a carboxylic anhydride group has anacid value of 1 to 80 mg KOH/g.
 15. The radiation sensitive compositionaccording to claim 13, further comprising a polymer-containing 50 mole-%or more of a repeating unit having a carboxyl group or a carboxylicanhydride group.
 16. The radiation sensitive composition according toclaim 1, wherein the dissolution rate in 2.38 weight-% aqueoustetramethylammonium hydroxide of the radiation sensitive composition isnot more than 5000 Å/min.
 17. The radiation sensitive compositionaccording to claim 1, wherein when the resin containing styrenicmonomer-repeating units of less than 50 mole-% of repeating units in theresin is used as the resin additive, the weight average molecular weightof the resin is 7,000 to 20,000 as determined by polystyrene standardsand when the resin containing styrene derivative-repeating units of notless than 50 mole-% of repeating units in the resin is used as the resinadditive, the weight average molecular weight of the resin is 3,000 to25,000 as determined by polystyrene standards.
 18. The radiationsensitive composition according to claim 13, wherein the value of Xwhich is B/A is in the range of 0.01 to 0.13 whereupon A is anintegrated area beneath peaks in the range of 7.2 to 5.6 ppm and B is anintegrated area beneath peaks in the range of 1.3 to 0.95 ppm in a¹H-NMR spectrum of a solution of the resin composition in heavy acetone.19. The radiation sensitive composition according to claim 1, whereinthe weight average molecular weight of the novolak resin is 3,000 to15,000 as determined by polystyrene standards.
 20. The radiationsensitive composition according to claim 1, wherein when a resincontaining styrenic monomer-repeating units of less than 50 mole-% ofrepeating units in the resin is used as the resin additive, the amountof the radiation sensitive material is 1 to 20 parts by weight relativeto 100 parts by weight of the alkali-soluble resin in the radiationsensitive composition and when a resin containing styrenicmonomer-repeating units of not less than 50 mole-% of repeating units inthe resin is used as the resin additive, the amount of the radiationsensitive material is 10 to 30 parts by weight relative to 100 parts byweight of the alkali-soluble resin in the radiation sensitivecomposition.
 21. The radiation sensitive composition according to claim20, wherein when the resin containing styrenic monomer-repeating unitsof less than 50 mole-% of repeating units in the resin is used as theresin additive, the amount of the radiation sensitive material is 1 to18 parts by weight relative to 100 parts by weight of the alkali-solubleresin in the radiation sensitive composition.
 22. The radiationsensitive composition according to claim 1, wherein when a resincontaining styrenic monomer-repeating units of less than 50 mole-% ofrepeating units in the resin is used as the resin additive, the contentof the resin additive is 1 to 20 parts by weight relative to 100 partsby weight of novolak resin of the alkali-soluble resin and when a resincontaining styrenic monomer-repeating units of not less than 50 mole-%of repeating units in the resin is used as the resin additive, thecontent of the resin additive is 0.5 to 5 parts by weight relative to100 parts by weight of novolak resin of the alkali-soluble resin. 23.The radiation sensitive composition according to claim 1, furthercomprising a low molecular compound having phenolic hydroxyl group orgroups represented by the general formula (I):

wherein R₁, R₂, R₃, R₄, R₅, R₆ and R₇ each represents independently H, aC₁ to C₄ alkyl group, a C₁ to C₄ alkoxyl group, a cyclohexyl group or agroup represented by the formula:

wherein R₈ represents H, a C₁ to C₄ alkyl group, a C₁ to C₄ alkoxylgroup or a cyclohexyl group; each of m and n is 0, 1 or 2; each of a, b,c, d, e, f, g and h is 0 or an integer of 1 to 5 satisfying a+b≦5,c+d≦5, e+f≦5, and g+h≦5; and i is 0, 1or 2.